Blue-Bak T414 Waterproof paper sheets - Exceptional finishing in wet sanding applications. Sharp silicon carbide abrasive provides exceptional finishes in wet applications. Strong resin bond for longer life in wet applications. High-strength B-weight waterproof paper backing is extremely flexible. Improved wet-curl resistance. Environmentally stable; resists humidity-caused curling. Typical applications include light-duty metal sanding, primer sanding, defect removal from painted surfaces, filler sanding, sanding and finishing of composites and fiberglass, bare wood sanding and sanding between sealer coats.